diff options
| author | H. Peter Anvin <hpa@zytor.com> | 2026-03-25 16:01:47 -0700 |
|---|---|---|
| committer | Borislav Petkov (AMD) <bp@alien8.de> | 2026-03-27 16:04:47 +0100 |
| commit | ac66a73be03a0a72aeeb33d3610cfc43cb101a0b (patch) | |
| tree | 0e4e0f4248a0336f5e5ca7d95ec97e996f512ad6 | |
| parent | c369299895a591d96745d6492d4888259b004a9e (diff) | |
x86/fred: Enable FRED by default
When FRED was added to the mainline kernel, it was set up as an explicit
opt-in due to the risk of regressions before hardware was available publicly.
Now, Panther Lake (Core Ultra 300 series) has been released, and benchmarking
by Phoronix has shown that it provides a significant performance benefit on
most workloads:
https://www.phoronix.com/review/intel-fred-panther-lake
Accordingly, enable FRED by default if the CPU supports it. FRED can of
course still be disabled via the fred=off command line option.
Touch up Kconfig help too.
Signed-off-by: H. Peter Anvin (Intel) <hpa@zytor.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Sohil Mehta <sohil.mehta@intel.com>
Link: https://patch.msgid.link/20260325230151.1898287-2-hpa@zytor.com
| -rw-r--r-- | Documentation/admin-guide/kernel-parameters.txt | 4 | ||||
| -rw-r--r-- | arch/x86/Kconfig | 2 | ||||
| -rw-r--r-- | arch/x86/kernel/cpu/common.c | 2 |
3 files changed, 4 insertions, 4 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 03a550630644..bfa8a20ccc37 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -1750,8 +1750,8 @@ Kernel parameters fred= [X86-64] Enable/disable Flexible Return and Event Delivery. Format: { on | off } - on: enable FRED when it's present. - off: disable FRED, the default setting. + on: enable FRED when it's present, the default setting. + off: disable FRED. ftrace=[tracer] [FTRACE] will set and start the specified tracer diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index e2df1b147184..876b663dcf38 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -557,7 +557,7 @@ config X86_FRED bool "Flexible Return and Event Delivery" depends on X86_64 help - When enabled, try to use Flexible Return and Event Delivery + When enabled, use Flexible Return and Event Delivery instead of the legacy SYSCALL/SYSENTER/IDT architecture for ring transitions and exception/interrupt handling if the system supports it. diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index a8ff4376c286..0b02cb038d7f 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -1746,7 +1746,7 @@ static void __init cpu_parse_early_param(void) /* Minimize the gap between FRED is available and available but disabled. */ arglen = cmdline_find_option(boot_command_line, "fred", arg, sizeof(arg)); - if (arglen != 2 || strncmp(arg, "on", 2)) + if (arglen == 3 && !strncmp(arg, "off", 3)) setup_clear_cpu_cap(X86_FEATURE_FRED); arglen = cmdline_find_option(boot_command_line, "clearcpuid", arg, sizeof(arg)); |